The invention relates to a multipart airbag cutting for an airbag of an occupant protection device for motor vehicles and to a method for producing an airbag from such an airbag cutting.
An airbag cutting of the generic type is designed to produce an airbag for an occupant protection device, which airbag is formed by at least two chambers which are separated from each other and which, after the inflation of the airbag, can be at a different pressure. The two chambers do not have to be separated from each other in an entirely gastight manner; rather, they may entirely communicate with each other by means of one or more openings in a corresponding partition. However, these openings have to be restricted in their cross section in such a manner that a different internal pressure can be maintained in the chambers at least for the period of time in which the airbag is to deploy its protective potential as a restraint device for a motor vehicle occupant.
The use of airbags having a plurality of chambers which differ in geometry and, in the inflated state, can have a different internal pressure is of significance, for example in the case of side air bags which may serve to protect the head, the thorax region, the abdomen region and the pelvis region of a vehicle occupant. For optimum protection of these different body parts from injury, airbag regions differing in geometry and having a different internal pressure are required in each case. Thus, for example, a chamber of the airbag that is provided for protecting the pelvis region is to have a greater internal pressure than a chamber provided for protecting the thorax region.
The invention is based on the problem of providing an airbag cutting of the type mentioned at the beginning and a method for producing an airbag from an airbag cutting of this type, which enable the production of an airbag, the chambers of which are connected stably to one another, using means which are as simple as possible.
This problem is solved in respect of the airbag cutting by the features of patent claim 1.
According to them, the airbag cutting has two airbag parts which, in the spread-out state, overlap each other and can be connected to each other in particular in the overlapping region, so that the overlapping region forms a boundary surface (partition) between two chambers of the inflated airbag, which can be produced by connecting the edges of the particular airbag cutting. Expressed in other words, each of the at least two airbag cuttings is firstly sewn or connected in some other manner along its outer edge in such a manner that an (open or closed) covering for a chamber of the airbag is formed from the particular airbag cutting; furthermore, the two airbag parts are additionally connected to each other in the overlapping region in such a manner that a partition (boundary surface) is formed between the two chambers and the two chambers can be supported stably on each other in this region.
The solution according to the invention has the advantage of enabling the production of a multichamber airbag from a two-dimensional airbag cutting in a simple manner, it also being possible to carry out the connections between the individual airbag parts of the cutting (by sewing) on the airbag, which is spread out flat and two-dimensionally, or on the airbag cutting which is in turn extended in one plane after sections of the airbag cutting are placed one over the other. The partition between the two chambers of the airbag produced from this airbag cutting is defined here in a simple manner by the overlapping region of the two airbag parts. The size of the overlapping region of the two airbag parts and the profile of the connecting points (connecting seams) between the two airbag parts also determines the stability of the airbag, in particular in respect of avoiding a tilting of the individual chambers toward each other. That is to say, the two airbag parts and the chambers, which are enclosed by the airbag in the inflated state thereof, can be aligned with respect to each other in a stable manner in the overlapping region, in which the two airbag parts are connected to each other.
In this case, the connecting line, along which the two airbag parts are connected to each other in the overlapping region, can annularly enclose the boundary surface between the two chambers of the airbag in the inflated state.
The connection of the two airbag parts in the overlapping region, in particular the connecting line annularly enclosing the partition (boundary surface) between the two chambers, can be formed, on the one hand, by additional connecting means, for example in the form of a seam or adhesive, or, on the other hand or in addition, by the fact that, in the inflated state of the airbag, a significantly higher pressure prevails in one chamber than in the other chamber, with the result that the first chamber is pressed along the connecting line toward the other chamber.
The connecting lines which are formed by additional connecting means, for example in the form of a seam, are provided by appropriate connection of the airbag parts forming the airbag cutting before the airbag is inflated. By contrast, the connecting lines formed by the differences in the internal pressure in the individual chambers of the airbag are not produced until the airbag is being inflated. The differences in pressure required for this can be produced in a known manner by a quantity of compressed gas that is required for producing the internal pressure desired in each case being introduced from the gas generator, which is used for inflating the airbag, into the corresponding chamber of the airbag.
The two parts of the airbag cutting are preferably designed and arranged in such a manner that, in the inflated state of the airbag, one part of the airbag cutting rests in a bell- or hood-shaped manner on the covering of the other, second chamber, the covering of the second chamber, including the boundary surface between the two chambers, being formed by the other, second airbag part.